Now that OHTS I has shown that topical ocular hypotensive medication is safe and effective in reducing the incidence of open angle glaucoma in moderate and high risk ocular hypertensive patients, it is important to determine when treatment should be initiated in ocular hypertension. The primary specific aim of OHTS II is to determine if there is a penalty for delaying treatment in ocular hypertension. The primary specific aim will be tested by comparing the long-term cumulative incidence of POAG and adverse events in the original observation participants in OHTS I who start treatment in OHTS II, to the long-term cumulative incidence in medication participants who received medication throughout OHTS I and who continue treatment in OHTS II (Primary Specific Aim) Secondary aims are: 1. To increase the precision and completeness of the risk model developed in OHTS I to predict which ocular hypertensive participants will develop POAG. 2. To determine the predictive accuracy of subthreshold visual field and optic disc changes for subsequent development of POAG. 3. To determine if there is a racial difference in treatment protection. Participants are followed twice yearly with automated threshold, central static perimetry (Humphrey 30-2) and once yearly with stereoscopic optic disc photographs. The study endpoints are reproducible optic nerve deterioration and/or reproducible visual field abnormalities attributable to POAG. We expect 90% of the 1,375 active participants in OHTS I to enroll in OHTS II. Participants will be followed for a minimum of 5 years with follow-up continuing until study termination as determined by the Data and Safety Monitoring Committee. As in OHTS I, the Study Chairman's Office and the Coordinating Center are at Washington University, St. Louis, MO. The Visual Field Reading Center is at University of California-Davis, Sacramento, CA, and the Optic Disc Reading Center is at Bascom Palmer Eye Institute, Miami FL. Clinical Centers are the same as in OHTS I. The protocol for OHTS II has been approved by the Executive/Steering Committee and the Full Investigative Group. All Clinical Centers and Resource Centers have received local IRB approval for OHTS II.